The end of theism.

[Act_of_Reparation]

82. Which doesn't really answer the question.

The assertion has been made that theism is a universal human behavior, that it has existed for as long as societies have existed. Evidence of "spirituality or cultic behavior in the Upper Paleolithic, and similarities in great ape behavior" does not support this claim, as "spirituality or cultic behavior" are not the same as belief in god or gods. Neither does this support the claim that these beliefs are universal, cross-cultural behavior.

Atheists exist, so theism is evidently not universal.

And that is part and parcel the problem with evolutionary psychology as a field. It's practitioners observe current behavior, assume it is biological in origin, and construct a completely unfalsifiable evolutionary explanation for its existence. We cannot go back in time and observe the development of human social behavior the way we can observe shifts in the frequency of alleles over time. There's nothing biochemical or molecular to observe and test, and there is no way to exclude sociological explanations for the same behaviors. There's very little hard science involved in the field and many are understandably skeptical of its conclusions, and wary of its potential applications (read Stephen Jay Gould's The Mismeasure of Man for a thoroughly depressing examination of biological determinism in practice).

The fact of the matter is we don't know when or how theism first emerged and, given our most ancient ancestors' unfamiliarity with writing, we are unlikely to find out. What we do know is a lot of people believe in deities, but also that those beliefs are largely informed by cultural or familial traditions.